Classical Music: Mauricio Kagel at 65 Queen Elizabeth Hall, London

The joker who is a poet and a critic has a time-honoured role. The Argentine-born composer Mauricio Kagel is nobody's fool. Over the past 20 years he has consistently spoken his own musical language with an air of mournful jollity. Regular rhythms creak and stutter like an ailing machine; there are a lot of chords, spaced closely at the extremes, as you're taught not to do in harmony lessons; and there's also a good deal of creeping movement in semitones, though unlike real chromatic harmony Kagel's sounds remain free from a sense of gravitational pull. All these features are deployed in fastidious instrumentation - and Kagel's requirements can be expensive for concert promoters, particularly in the percussion department.

But there is a bit of the boyo about him, too. "West", the last of his eight Windrose pieces for small salon orchestra, which opened the London Sinfonietta's 65th birthday concert on Sunday night, has its end signalled by the percussionist chopping a log. And a documentary vocal cycle chronicling events on the day of Kagel's birth, ..., den 24.XII. 1931, has one of its two percussionists running amok and riffling the pages of a book for the sound it makes. That particular item was suggested by the collapse of a roof in the Vatican Library.

At his best, Kagel transforms recognisable elements of existing music and creates something new, weird and beautiful. "West" comments on the fact that blacks, in effect, colonised the whites with their music, and questions the concept of cultural purity. At times it evokes one of those rowdy paintings of Harlem by Edward Burra, in reconstituted jazz. It starts well, in a very detached unjazzy manner, but the nearer it gets to its subject the less interesting it becomes. There's a disturbing and frustrating sense of the arbitrary, as if there's an undisclosed programmatic basis.

The birthday piece, which the commanding baritone Roland Hermann sang at the centre of the concert, has a beautifully gloomy opening, which you could interpret as a humorous gesture of self-denigration. But Kagel sails close to the wind when the Japanese commander-in-chief barks his threats to purge the North Manchurian city of Ch'en-ch'ing to kitschy pseudo-oriental chopsticks music. Well, Kagel has never been afraid to risk accusations of poor taste, and he would no doubt argue that the shock of the text needs to be matched. It just seems a failure of imagination, a bit obvious, as does the following number, where a ghostly march accompanies an advertising slogan, "The National Socialist smokes only Parole", delivered by the baritone in wheezy tones.

Still, a letter from a homesick German immigrant in Argentina (Kagel himself moved in the opposite direction, and has lived in Germany for 40 years) calls forth some wonderfully characteristic grumbling instrumental textures. And the final number has a skilful pile-up of bell effects, till undermined by a tape of real church bells.

The newest piece played on Sunday was Orchestrion-Straat, which Kagel finished this year. Here the players were seated two by two, in a diagonal line across the stage, rather like the animals lining up for Noah's Ark. The conductor, Reinbert de Leeuw, directed from their front, to the audience's right. Orchestrion-Straat is a 21-minute homage to the automatic music machines still found in the streets of Holland, or so they say. Kagel's music is raucous and bottom-heavy with double-basses and tubas, yet the daintier instruments, the flutes and violins, can be heard as well. The actual music is a riotous jumble only suggesting the atmosphere of popular music without ever slipping into pastiche. Very clever.